Drum magnet separator



June 21, 1955 E. A. LAURILA DRUM MAGNET SEPARATOR Filed May 20, 1954 4Sheets-Sheet 1 Inventor ERRKI. A. LAURILA 7 5 Hrs ATTOR EYS June 21,1955 AUR|| A 2,711,249

DRUM MAGNET SEPARATOR Filed May 20, 1954 4 Sheets-Sheet 2 Inventor?ERRKI LAURILA M PV LQ HIS ATTORNEYS June 21, 1955 E. A. LAURILA2,711,249

DRUM MAGNET SEPARATOR Filed May 20, #1954 4 ShQe ts-Sheet 5 H97 ,F f 1 W5 iii v, 1% 'J.

l l J Inventor:

ERRKI A. LAURILA HIS ATTORNEYS June 21, 1955 E. A. LAURILA DRUM MAGNETSEPARATOR 4 Sheets-Sheet 4 Filed y 20. 1954 III .lm enzorz' ERRKI A.LAURILA' ls ATTORNEYS United States Patent 0 DRUM MAGNET SEPARATOR ErrkiA. Laurila, Helsinki, Finland, assignor to Aktiengesellschaft fiirUnternehmungen der Eisenund Stahlindustrie, Essen, Germany, acorporation of Germany Application May 20, 1954, Serial No. 431,210 6Claims. (Cl. 209-219) Various kinds of drum magnet separators have beenknown for carrying out a magnetic separation of finely divided magneticmaterials into magnetic and non-magnetic constituents. The magneticfield of these separators may be produced by means of a multipolarmagnet system which is either fixed within a rotating drum cover orrotates in synchronism therewith. As is known, it is the function of themagnetic field to hold the magnetic particles fast to the drum coverwhile the non-magnetic particles are carried away by reason of gravity,centrifugal force or by rinsing or blowing off.

In the case where a slowly rotating separator with fixed magnets isused, it has been shown that the separating effect is particularly poorif the magnetic field is formed either by direct current magnets orpermanent magnets, because in such cases the finelydivided particlestend to roll together upon the drum cover to form dense accumulations.For this reason magnetic separators have heretofore been constructedwhose magnet system displays alternating polarity in the direction ofwork, or rotates, or is driven by alternating current.

However, all such previous devices have been either too complex,expensive and difficult to manufacture or have not been able to providea uniform magnetic field, or have had other difliculties. The presentinvention which overcomes the above disadvantages, relates to a drummagnet separator whose construction is based upon theoretical andpractical investigations concerning the effect of a magnetic field uponfinely divided magnetic material. These investigations have led, amongothers, to the following conclusions:

1. The best results are obtained when the magnetic field produces anattractive force, directed against the drum cover and acting upon themagnetic particles, which is distributed as uniformly as possible overthe entire separating surface.

2. The movement of the magnetic field with respect to the drum covermust be so chosen that the magnetic particles lie loosely with respectto each other. Theoretically considered, only those magnetic fields areadapted for practical use, whose field strength vectors appear to berotating with respect to a given point upon the drum cover. If,simultaneously, the magnetic attractive force, referred to above, is asuniform as possible, then the field vector will turn rather uniformly.The magnetic particles have a tendency to retain their polarity due tothe hysteresis phenomenon, so that they are put into a turning movement.Since the magnetic field simultaneously pulls the particles against thedrum cover, the particles will roll off the cover. So long as thecircumferential speed of the magnetic field is small, the particles willroll in the form of magnetic accumulations; if, however, thecircumferential speedexceeds a certain value, then the particles willroll individually.

A magnetic field that fulfills the requirements set forth above may beproduced without great difiiculties if one employs a multipolar magnethaving at least 12 and preferably 32 to 48 magnet poles, whereby thepoles 2,71 1,249 Patented June 21, 1955 underlie the drum cover andalmost tween the drum cover, and the drum. The poles should be,furthermore, so magmetized that north and south polarities alternatewith each other.

For this construction permanent magnets are better suited thanelectromagnets.

In order to attain a sufiicient field strength at the outer surface ofthe drum cover, it is necessary to form the drum in such a manner thatthe distance between the magnet poles or pole shoes and the outersurface of the drum cover is as small as possible. In order that thenecessary requirements are fulfilled, the 'magnet must cover the entirecircumference of the drum. Furthermore, the magnet must be able to turnindependently of fill the space bethe turning of the drum, because thedifference between the circumferential speed of the magnet field andthat of the drum cover is determinative of the loosening up of theaccumulations of magnetic particles.

Several magnetic separators according to the invention are illustratedbyway of example in the drawing.

Fig. 1 shows a side view of a magnetic separator and a schematicrepresentation of the individual parts.

Fig. 2 shows the same separator with a different arrangement ofindividual parts.

Fig. 3 is a partly sectional and partly elevational side view of amagnetic drum embodying the invention.

Fig. 4 is a partly sectional and partly elevational view of thestructure of Fig. 3 taken perpendicular to the view of Fig. 3.

Fig. 5 is a cross-sectional view showing the details of the magnetsystem.

Fig. 6 is a sectional view perpendicular to Fig. 5.

Figs. 7 and 8 are elevational views showing two kinds of drum units.

Fig. 9 represents a magnet drum consisting of a plurality of drum units,section and the lower half in elevation.

Fig. 10 is an enlarged sectional view of a unit of the magnet system ofthe drum shown in Fig. 9.

Referring in greater detail to the drawings, the casing of the magneticseparator comprises two chambers 1 and 2 which extend downward in theshape of a funnel. In chamber 1 is arranged the magnetic drum, whichconsists of the drum cover 3 and the magnetic system 4 enclosed therein.The drum cover and the magnetic system are rotatably mounted upon theshaft 5; they may, as indicated in Fig. 1, rotate in the same directionand with different speed, or also in opposite directions.

Above a separating wall 6 arranged between the chambers 1 and 2 there isprovided a removal cylinder 7 composed of .soft iron which rotates inopposite directions to that of the magnetic system 4, but preferablywith the same circumferential speed as the latter, and is provided withknife-shaped cleats radial to the cylinder axis 8 or with pointedprojections uniformly distributed upon the surface of the. cylinder 7,whereby the magnetic material that is supplied to the magnetic drum 3,and held fast thereon, is taken otf from the drum. The supply ofmaterial is elfected through a chute 10, which, according to Fig. 1-,has its lower end extending between the magnetic drum and the removalcylinder thereby also serving as a deflecting wall for the material thatis thrown off the removal cylinder. As shown by Fig. 2 the supply chute11 and the deflecting wall 12 may also bearranged independently of eachother.

The material supplied to the drum cover 3, that rotates in the directionof the arrow, is carried along thereby. The nonmagnetic constituentsfall' off the cover and are removed from the funnel 13', while themagnetic constitnents are carried along by the drum cover, are removedby the cylinder 7, and are drawn off. through the funnel 14.

the upper half being in longitudinal I Above the drum cover 3, blowingnozzles are provided through which air is blown against the materiallying on the cover in order to bring about a further loosening up of thematerial, whereby the separation into magnetic and non-magneticconstituents is supported.

Preferably a suction tube 16 is arranged at a suitable location in thechamber 1, through which the dust developed during the operation iscontinually drawn off.

In the following there is described a separating drum embodying theinvention.

Upon the shaft 5 there is afiixed a disc 17 whose flange 18 consists ofa material having good magnetic conductivity, for example, of acarbon-free steel. Upon the flange there are arranged in uniformdistribution and in even numbers the pole pieces 19, at least 12 innumber and preferably between about 30 and 48. One should choose thegreatest possible numbers of pole pieces in order to obtain a magneticfield of the most uniform strength, since such a field is the mostfavorable for producing a rolling movement of the particles upon thedrum cover. The pole pieces may be electro-magnetically actuated or theymay be formed of permanent magnets. The cross section of the polepieces, in the case of permanent magnets, preferably increases towardsthe middle of the drum, and the side wall of the pole pieces areoutwardly bent surfaces (compare Fig. 5). The pole shoes 20 are providedupon the outwardly lying front sides of the pole pieces and theselikewise consist of a material having good magnetic conductivity, forexample, of a carbon-free steel. The outer surface of the pole shoes ispreferably formed cylindrically or polygonally.

Upon the axle 5 there is mounted on each side of the disc 17 a disc 21and 22 respectively, these discs'being loosely rotatable. The discs 21and 22 carry at their circumference, the drum cover 23 which is composedof a 5 non-magnetic material, for example, of austenitie steel, Germansilver or synthetic resin, having a high electrical resistance and athickness of at most, about 2 mm. preferably 0.5 to 0.8 mm. The thinnerthe cover, the stronger is the effective magnetic field and the morecertain are the otherwise occurring vortex currents avoided. Theattachment of the drum cover to the discs 21 and 22 may be made in anydesired suitable manner, for example, by screwing, welding, soldering,gluing and the like.

To the axle 5 there is connected a driving disc 24 and to the extendedhub 25 of the disc 21 there is connected a driving disc '26, so that thedrum cover and the magnetic system surrounded thereby may be rotatedindependently of each other.

The pole pieces 19 with the pol e shoes 20, that are loosely inserted inthe flange 18, are firmly fixed to flange 18 by detents 27 whichclampingly engage two adjacent pole shoes, these detents consisting ofnon-magnetic material, and being mounted on screws 28. Of course, thereare other means for attaching the pole shoes such as, for example, theuse of swallow tail shaped grooves in the flange 18, within which thecorrespondingly shaped pole shoes are fitted, as well as welding,soldering, or s n The provision of the drum cover is particularlyimportant for the most effective operation of the magnetic separatoraccording to the invention. In order to attain a high field strength atthe entire surface of the cover it is necessary that the same distancebe maintained between the inner surface of the cover and the pole shoesat all points, which distance is to be maintained as small as ispossible. This distance should not be allowed to either decrease norincrease upon rotation of the drum cover, so that the drum cover despiteits slight thickness must have a suflicient solidity and above 'all mustbe substantially unbendable. In order to attain this, the circumferenceof the drum cover must be smallin relation to the diameter of the drum.As an example for this, there may be mentioned a drum cover'consistingof a 0.8 mm. thick austenitic rust-free steel sheetwith a diameter of400 mm., which should have a circumference no longer than 150 mm., andpreferably only mm. long. Since, however, a magnetic separator having soshort a drum cover would result, in a great majority of cases, in toosmall a capacity, according to the invention several such drums may bemounted upon the common driving shaft independently and spaced at smalldistances from each other (Figs. 7 and 8). In the embodiment, accordingto Fig. 7 there lies at one end of the driving shaft 5 the driving disc29 for all magnetic systems, while for driving the drums 3t), 31 and 32there is provided ineach case a driving disc 33, 34 and 35. In theembodiment according to Fig. 8 there is also provided for all drums acommon driving disc 36. This is rendered possible because the drums areconnected with each other by means of bolts 37.

The separating drum assembly of Figs. 9 and 10 dif- I fers from that ofFigs. 7 and 8 in that not several individual drums lie side by side, butthat all magnetic systems are surrounded by a common cover 38, which is,

supported by intermediate discs 39 between the individual magnet systemsand by end discs 40, 41. This embodiment is substantially simpler andcheaper than the one of Figs. 7 and 8, and, furthermore, has theadvantage that the drum cover may at any time, be tightened from one ofthe two front sides.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed in this invention is:

l. A magnetic separator for separating magnetizablc particles fromunmagnetizable particles comprising a rotatable drum consisting of arotatable disc, a rotatable annular cover member mounted coaxially withsaid disc in spaced relation thereto, said'disc and said cover memberbeing arranged to rotate independently of each othensaid cover memberbeing constructed of a dielectric material, a plurality of pole piecesmounted between said disc and said cover member, the space between saiddisc and said cover member being annularly uniform and having, apredetermined minimum width.

2. The separator of claim 1 wherein the thickness of said cover memberdoes not exceed about 2 mm.

3. The separator of claim 1 wherein the pole pieces member coaxial withsaid inner member, a plurality of radially'extending magnetic polepieces between said inner and outer members, and a cylinder rotatablymounted adjacent said drum, said cylinder being adapted to re tate atthe same speed but in the opposite direction relative to said drum, saidcylinder having means on the pcriphery thereof for removing magneticallyheld particles.

from said drum.

5. The separator of claim 1 wherein a plurality of said.

drums arearranged laterally of each other on a common axle, said discsbeing connected to said axle for rotation therewith, and said covermembers being loosely mounted on said axle, there being separate drivingmeans for said axle and for said cover members.

6. The separator of claim-l wherein a plurality of said discs arearranged laterally of each other on a common driving shaft, a commoncover member overlying all of 7 said discs, and means to rotate saidcover member separately from said discs.

No references cited.

1. A MAGNETIC SEPARATOR FOR SEPARATING MAGNETIZABLE PARTICLES FROMUNMAGNETIZABLE PARTICLES COMPRISING A ROTATABLE DRUM CONSISTING OF AROTATABLE DISC, A ROTATABLE ANNULAR COVER MEMBER MOUNTED COAXIALLY WITHSAID DISC IN SPACED RELATION THERETO, SAID DISC AND SAID COVER MEMBERBEING ARRANGED TO ROTATE INDEPENDENTLY OF EACH OTHER, SAID COVER MEMBERBEING CONSTRUCTED OF A DIELECTRIC MATERIAL, A PLURALITY OF POLE PIECESMOUNTED BETWEEN SAID DISC AND SAID COVER MEMBER, THE SPACE BETWEEN SAIDDISC AND COVER MEMBER BEING ANNULARLY UNIFORM AND HAVING A PREDETERMINEDMINUMUM WIDTH.